Java Servlet API Frequently Asked Questions Answers

Java Servlet API Frequently Asked Questions Answers Question: What is Java Servlet API? Answer: Java Servlet API is a Java programming interface (API) for building a web application.It allows developers to write Java -based web applications and provide Web services through the Servlet container (such as Tomcat). Question: How to create a Servlet? Answer: To create a service, you need to execute the following steps: 1. Create a Java class that expands javax.servlet.httpStpservlet class. 2. Rewill the doget () or dopost () method in the class to process HTTP GET or Post requests. 3. Configure the service mapping in the web.xml file, and specify the name and URL mode of the service. The following is a simple sample code, demonstrating how to create a HelloWorldServlet: import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class HelloWorldServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.getWriter().print("Hello, World!"); } } Question: How to handle the GET and Post request parameters of Servlet? Answer: You can use the httpservletRequest object to access the service parameter of the Servlet.Here are examples of processing GET and Post request parameters: protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String name = request.getParameter("name"); response.getWriter().print("Hello, " + name + "!"); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String name = request.getParameter("name"); response.getWriter().print("Hello, " + name + "!"); } Question: How to redirect a Servlet request (redirect)? Answer: You can use the SendRedirect () method of the HTTPSERVLESPONSE object to redo the service request.The following is an example code: protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.sendRedirect("https://www.example.com"); } Question: How to use session in service? Answer: Servlet can use the GetSession () method of the HTTPSERVLETREQUEST object to obtain an HTTPSession object to track session information.The following is an example code: protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); session.setAttribute("username", "john"); } Question: How to read and set cookies in Servlet? Answer: Servlet can use the GetCookies () method of the HTTPSERVLETREQUEST object to obtain the cookie array and use the AddCookie () method of the HTTPSERVLESPONSE object to set the cookie.The following is an example code: protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Cookie cookie = new Cookie("name", "john"); response.addCookie(cookie); } Question: How to deal with the abnormality of service? Answer: You can use the TRY-CATCH block to capture the abnormalities in Servlet and deal with them as needed.The following is an example code: protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { // Business logic code } catch (Exception e) { response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "An error occurred"); } } I hope these common questions can help you better understand and use the Java Servlet API.If you have any other questions, please ask at any time!